US1932933A - Printing telegraph exchange system - Google Patents

Description

Wet. 31, 1933; F. s. HALLDEN 4 PRINTING TELEGRAPH EXCHANGE SYSTEM Filed Nov. 5, 1931 2 Sheets-Sheet 1 INVENTOR FREDERICK G. HALLDEN BY 1% ATTOR EY .Oct. 3l,'193 F. G. I-IALLDEN PRINTING TELEGRAPH EXCHANGE SYSTEM Fil d N V- 1931 2 Sheets-Sheet 2 I I I l l I I l l I I I I I I I l I l l l l I l l l l l I I I I l l I l .IIIIIIIIhm:IIIIIIIIIIIII IHI" III-

| l l l I|I||||l| ||ll IIIIIIIIIIIIIIIIIIII lllllllll r I I I I I I I I I I l I I I I I I I I I I I I l I I I I I I I I I I N E D L M G K m R E D E R F Patented Oct. 31, 1933 1,932,933 PRINTING TELEGRAPH EXCHANGE SYSTEM Frederick G. Hallden, Bellerose, N. Y., assignmto International Communications Laboratories, Inc., Newark, N. J., a corporation of New York Application November 6, 1931. Serial No. 573,323

10 Claim.

This invention relates generally to step-bystep switches, and more particularly relates to step-by-step switches that can be employed interchangeably asline finders or as connectors.

In automatic printing telegraph exchange systerns that provide automatic switches for interconnecting any one of a plurality of subscribers stations with an operators position at a central station, it is frequently desirable to equip each operators position for both sending and receiving. With the ordinary type of stepby-step switches this can be done only by associating with each operators position both a line finder and a connector switch.

The object of the present invention is to eliminate one of these two switches by providing a step-by-step switch that can be used interchangeably as a line finder or as a connector.

Another object is to provide a switch of such construction that it can readily be grouped with other similar switches in a manner well-known in the art, for the purpose of increasing the efiiciency of each of the switches in the group.

According to this invention, a plurality of subscribers stations and the operators positions at a central station are associated through a group of combination line finder-connector switches, each switch being individual to an operators position for outward service. A sequence switch pre-selects an idle switch in the group to answer the next call from a subscribers station. When a call occurs an interrupter, common to the group of switches, is caused to step the selected switch until the calling line is found. The subscribers line is thereupon connected through the operated switch to the associated operators set, the interrupter is dis-associated from the switch, and the sequence switch prepares the next idle switch to answer a subsequent call.

When a combination switch is used as a connector it is directively controlled by an associated operators set, in the usual manner, to establish connection to one of the subscribers stations.

Means are provided, while a combination switch is in use as a line finder, for making it busy to the associated operators set, and while it is in use as a connector, for making it busy to the subscribers stations.

Referring now to the drawings, in which Fig. 1 should be placed above Fig. 2 to show the arrangement of the elements of the system, Fig. 1 discloses a subscribers station W, a combination line finder-connector switch X; and Fig. 2

discloses a sequence switch Y, and an operators set Z at a central station. It is to be understood that in actual practice a number of subscribers stations (but not more than 100) would be multiplied to the bank terminals of the switch X, and to the terminal banks of other similar switches (not shown) to permit connection between any one of the subscribers stations and any one of the operators sets, such as at the central station. The sequence switch Y is shown as a ten point switch, but it is to be understood, that it may be provided with a number of contacts sufficient to provide connection to any desired number of operators sets.

The apparatus at the subscribers station W and the central operator's set Z are similar to the apparatus disclosed in U. S. Letters Patent No. 1,895,112, granted toG. S. Vernam. The line wire 1 from the subscribers station W terminates at the central oflice in a line relay 2. The line relays are divided into groups, there being ten groups to each one hundred lines. A group relay'3 (Fig. 2) is common to each group of ten line relays, so that when any line relay is energized, the group relay associated with it is also energized. The group relay, 'when operated, marks, or renders selectable, the level contact of the vertical commutator 8 in a predetermined idle combination switch, while the line relay, when operated, marks the individual test contact 20 in that switch. The sequence switch Y, which is common to the combination switches, is caused to rotate whenever a combination switch has found a calling line. In rotating sequence switch Y picks out an idle combination switch, such as X, thus conditioning that switch to answer the next call from the group of one hundred subscribers lines. On the shaft (not shown) of the switch X are mounted a private wiper 4, a line wiper 5, and a test wiper 6. These wipers move over contacts in the private line and test banks respectively of switch X when that switch rotates. Also mounted on the same shaft (not shown) is a vertical wiper '7 which moves over the contacts in the vertical commutator 8 of the switch X when that switch is stepped vertically. Upon the operation of the group relay, assuming that combination switch X has previously beenselected by sequence switch Y, switch X first steps vertically to pick out the group of calling lines, and then rotates horizontally until the calling line is found. When the switch X is first operated a guard lamp is operated at the operators set Z.

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When the calling line is found this line is made busy at each of the other combination switches, the current in this line is reversed thus causing the subscriber's printer motor to be started and the current in the line circuit increased to its signalling value. Telegraphic communication can then be carried on between the calling subscriber W and the operators set Z. At the same time the sequence switch Y is operated to associate another idle combination switch with the group of 100'subscribers lines. When communication has ended, the central station operator releases the combination switch X and dis-establishes the connection.

When the combination switch X is employed as a connector, in establishing a connection between a central station set Z and the subscribers station W, the key 9 is operated to connect the dial 10 to the dial lead 11 and to the slowrelease relay 12. This relay thereupon energizes grounding the contact corresponding to switch X on the lower bank of sequence switch Y, thus making switch X busy and preventing its seizure by a calling line. The switch X is then operated by dial impulses, in the usual manner, to establish connection with subscribers station W. When connection is established the operator at Z reverses the current over the subscriber's line 1, starting the printer motors at the subscriber's station W. As the operator's printer motor (not shown) is running continuously, telegraphic communication can then be carried on. mentioned above, is under the control of the central station operator.

The detailed operation of the system is as follows: to make an inward call the subscriber at W operates the key 13 to shunt-the lower or high resistance winding of the line relay 14. The removal of this high resistance from the line circuit causes the line current to increase to a value which operates the line relay 2 at the associated central station over a circuit from grounded negative battery, winding of line relay 2, contact B of the cut-off relay 15, equalizing resistance, upper winding of polar line relay 14, contact of calling key 13, transmitter 16, printer magnets 17, break key 18, and to ground. As polar relay 14 is wound so as to close its contact only in response to positive current, the circuit of motor control relay 19 remains open. The operation of line relay 2 completes at its A contact an obvious circuit for operating the associated group relay'3, and at its B contact connects ground to the test bank contact, corresponding to the calling line, in each of the combination switches, such as contact 20 of switch X. The group relay 3 is multiplied by conductor 51 to contacts A of other line relays associated with the subscribers lines to which group relay 3 is common.

Assuming now that the sequence switch Y has previously been operated to prepare combination switch X to answer the next call, the operation of group relay 3 completes two circuits for controlling the extent of the vertical and horizontal movements of switch X, and another circuit for effecting the movement of that switch into engagement with the calling line 1. At its A contact, group relay 3 completes a circuit for determining the extent of vertical movement of all of its associated switches, such asX, though, of course, only the switch X, selected by the sequence switch Y, will be operated. The circuit to switch X may be traced from negative bat- The release of the connection, as.

tery, winding of interrupter control relay 21, contact A of relay 3, to the segment of the vertical commutator 8 corresponding to the level in which the contacts of the calling line appear. Similarly, negative battery is extended to a corresponding segment in the vertical commutator bank of each of the other associated switches (not shown) over conductor 50. At its B contact, relay 3 extends a parallel circuit, including the above-mentioned battery and winding of relay 21, through a contact in the upper bank of sequence switch Y to the test wiper 6, which co-operates with the test bank of switch X. Relay 3 also extends a circuit controlled by the interrupter 22, from ground, through the interrupter contacts, contact C of relay 3, a contact on the middle bank of sequence switch Y, contact B of relay 23 of switch X, upper and lower windings of relay 24 of switch X in series, to grounded negative battery. Conductors 49 extend to the B and C contacts of other associated group relays, so that any of such relays can upon operation complete circuits similar to the two circuits last traced. The interrupter pulses, which are of approximately dial frequency, then cause the contacts of relay 24 to-vibrate. The first closure of contact B of relay 24 causes slow-release relay 25 to energize over an obvious circuit. The first succeeding closure of contact 0 of relay 24 causes vertical magnet 26 to energize over a circuit from grounded battery, winding of vertical magnet 26, winding of slow-release relay 27, contact B of off-normal contacts, contact 0 of relay 25, contact C of relay 24 to ground. The switch X then takes one vertical step, thus opening contact B and closing contacts A and C of the cit-normal contacts 42, thereby extending the circuit of vertical magnet 26 through contact A of the off-normal contacts and contact B of slow-release relay 27. Relay 2'? and relay 25 remain operated when energized by pulses of dial frequency.

At the time that relay 2'7 was operated, switching relay 28 at the operators set Z was operated over a circuit extending from grounded battery, winding of relay 28, contact A of key 9, contact A of relay 24, contact A of relay 27 to ground, and the circuit of the guard lamp 29 was completed from grounded battery, guard lamp 29, and through contact A of key 9 over the remainder of the circuit above traced. Guard lamp 29 lights informing the operator that switch X has been seized. The switching relay 28 connects ground on release key 30 through contact E of the switching relay to release trunk 44, thus preparing a circuit for preventing the switch from releasing after the calling line has been found. The switching relay 28 also locks through its F contact to ground on the release key 30. The switching relay 28 at its B contact also connects the line circuit 31, through the winding of polar relay 32, transmitter 40, resistance and positive battery to ground.

Succeeding pulses from the interrupter 22 step the switch X vertically by operating the vertical magnet 26. As the switch steps vertically the private wiper 4, the line wiper 5, and the test wiper 6, are brought into alignment with successive levels on their banks and the vertical wiper 7 is carried over the contacts of on the segment corresponding to the operated group relay 3. When the vertical wiper 7 reaches this segment the circuit of relay 21, previously traced to this segment, is extended through the vertical wiper I, contact D of relay 2'7, contact C of operator's key 9 to ground. At the same time, private wiper 4, line wiper 5, and test wiper 6 are brought into alignment with the level of their respective contact banks in which the calling lirre contacts appear. Relay 21 then operates, shunting the interrupter contacts, thus holding relay 24 operated.

The pulsing circuit through the windings of relay 27 and the vertical magnet 26, being now open at contact C of relay 24, the vertical magnet 26 releases, and after an interval relay 27 also releases. The release of relay 2'? extends the pulsing circuit in parallel to the rotary magnet 33 and the slow-release relay 34. The release of relay 27 also opens at its D contact the circuit of relay 21, whereupon this relay releases, opening the shunt around the interrupter contacts. Relay 24 again responds to the interrupter pulses, which are now efiective to rotate the shaft (not shown) of the switch X. As the private wiper 4, the line wiper 5, and the test wiper 6 have been previously brought into alignment with the level of their respective contact banks in which the calling line contacts appear, the rotation of the shaft of switch Y, moves the several wipers over the contacts in the same level of their respective contact banks. On each level there are ten contacts, each corresponding to a subscribers line, and the several wipers are adapted to move over the ten contacts on the same level in their respective banks. In the present case, depending upon the position of the contacts correspondingto station A on the level, the switch wipers will be successively stepped until they come into contact with the bank contacts corresponding to the calling line.

When these bank terminals are reached a circuit is closed for operating relay 21, which circuit may be traced from battery, through the winding of relay 21, contact B of relay 3, contact of upper bank of sequence switch Y, test wiper 6, test bank contact 20 to ground on contact B of line relay 2. Relay 21 then operates, again shunting the interrupter contacts to hold relay 24 operated. The switch X is thus brought into association with the contacts of the calling line. During the rotary series of impulses, relay 34 is held operated. A short interval after the end of this series of pulses, relay 34 releases. A circuit is thereupon closed for operating outoff relay 15 and relay 23 in series. This circuit may be traced from grounded battery, winding of cut-ofi relay 15, private wiper 4 of switch X, contact B of relay 34, lower winding of relay 23, contact B of relay 35, contact A of relay 25, and to ground. The operation of relay 15 disconnects the subscribers line 1 from the line relay 2 and connects it to the line bank contact of switch X. The line relay 2 thereupon releases. The release of line relay 2 removes ground from group relay 3 and from relay 21, releasing these relays. This dis-associates the interrupter'circuit from the group of switches associated with sequence switch Y. Only contact F of relay 23, which is nearest to the core, is closed by the energization of the lower winding of that relay, but the closure of contact F completes a locking circuit from battery, upper winding of relay 23, contact F, contact B of relay 25 to ground. Relay 23 then completely operates. Contacts H and I, in opening, break the circuits of the rotary magnet 33 and the release magnet 36 respectively. The closure of contact G of relay 23 extends the line circuit 1 through contact B of switching relay 28. winding of relay 32, transmitter 40, to grounded positive battery. The closure of contact E of relay 23 connects ground to the cut-off relay 15, holding that relay operated, and connects ground to conductor 37, multipled to the private bank contacts corresponding to the calling line, in each of the other combination switches, thus, in a manner to be described later, making the calling line busy to calls from the central omce. The closure of make-before-break contacts 0 of re lay 23 transfers the winding circuit of relay 24 from the interrupter controlled ground, to ground on the release trunk 44 from release key 30.

The closure of contact A of relay 23 completes a circuit for operating greatly 38 of sequence switch Y which may be traced from grounded battery, winding of relay 38, contact of stepping magnet 39, contact of the lower bank of the sequence switch Y to ground on contact A of relay 23. Relay 38 then operates, connecting ground to the stepping magnet 39. Energization of the stepping magnet 39 opens the circuit to relay 38, and the release of this relay in turn effects the release of the stepping magnet 39. The release of stepping magnet 39 causes the wipers of sequence switch Y to advance one step. This reciprocal action between the relay 38 and the stepping magnet 39 causes the sequence switch Y to step from one terminal to the next until a terminal is reached which is associated with an idle line finderconnector switch. When the sequence switch Y has stepped to such a position, the circuit through the lowest wiper of the sequence switch is no longer grounded, that is, it is grounded neither at contact A of a relay, such as 23, in the idle combination switch selected nor at contacts of the slow-release relay l2. Relay 38 thus remains released, at this position of the sequence switch, and its release prevents the reenergization of the stepping magnet 39. The combination switch now in connection with the sequence switch Y is thus conditioned to answer the next call from the group of one hundred subscribers stations.

When the calling subscribers line 1 was extended to positive battery through relay 32, the current was reversed in the subscribers line circuit 1. In response to this current reversal, the polar line relay 14 at the subscribers station W operates, effecting the operation of motor control relay 19. The operation of this last mentioned relay starts the subscribers printer motor 41, and shunts the lower or high resistance winding of the line relay 14. Calling key 13 should be released when the motor starts. Up to the time the line 1 was extended through the winding of relay 32 by the operation of switching relay 28, relay 32 was included in a local circuit to ground to keep the circuit of the printer magnets 42 closed. The line circuit is now completed from grounded positive battery, transmitter 40, winding of relay 32, contact B of switching relay 28, contact G of relay 23, line wiper 5, contact A of cut-off relay 15, upper winding of line relay 14 at station W, contact of motor control relay 19, transmitter 16, printer magnets 17, break key 18 to ground.

As the printer motor (not shown) at the central station set Z is running continuously, telegraphic communication can now be carried on between the subscribers station W and the central ofiice operators set. After the message has been transmitted, the central ofllce' operator releases by operating the release key 30, thus removing ground from the winding of switching relay 28 and from the release trunk 44. Switching relay 28 thereupon releases, extinguishing the guard lamp 29, and applying negative battery through contact E of key 9 and contact C of relay 28 to the line circuit 31. The removal of ground from the release trunk 44 releases relay 24 of switch X. Release of relay 24 deenergizes relay 25, which in turn opens both windings of relay 23. Relay 23 releases and at its A contact removes ground from the contact on the lower bank of the sequence switch C; at its make-before-break contacts C disconnects relay 24 from the release trunk 44; at its E contact opens the circuit of cut-off relay 15 and removes ground from conductor 37, at its G contact disconnects the line extending to operators set Z from the line wiper 5; at its I contact closes the circuit of the release magnet 36 from grounded battery, winding of the release magnet 36, contact I, off-normal contact C, contact D of relay 25, contact C of relay 24 to ground. The release magnet 36 operates, restoring switch X to normal. The release of the cutoff relay l5 reconnects the subscribers line 1, through the line relay 2 to negative battery while the removal of ground from conductor 37 removes the busy condition from the private contacts of station W in the other switches.

The reversal of current on the subscribers line 1, cause polar line relay 14 to de-energize motor control relay 19. The release of the motor control relay stops the subscribers printer motor and cuts the lower and high resistance winding of relay 14 into the line circuit. All circuits are thus restored to normal, and the next idle combination switch is conditioned, by sequence switch Y, to answer the next call from a group of 100 subscribers lines.

To make an outward call, the central station operator, at Z, throws the dial key 9 to the centre position (note that this key is shown operated to the right), thus establishing a circuit for operating slow-release relay 12, and for intermittently operating relay 24 of switch X by means of dial 10. This circuit may be traced from grounded battery, both windings of relay 24 in series, winding of relay 12, dial lead 11, busy lamp 45, contact D of switching relay 28, contacts of dial 10, contact B of key 9 to ground. Relay 12 operates, grounding the contact corresponding to combination switch X in .the lower bank of sequence switch Y, thus preventing a calling line from interfering with that switch and stepping the sequence switch, as previously described, until its wipers engage the contacts of the next idle combination switch. Relay 24 also operates, closing an obvious circuit for slow-release relay 25. Relay 25 prepares a pulsing circuit for the vertical magnet 35, which circuit, when completed, extends from battery, winding of vertical magnet 26, winding of relay 27, contact B of off-normal contacts 42, contact C of relay 25, to grounded contact C of relay 24. After the first vertical movement of the switch the pulsing circuit is transferred through contact B of relay 27, and contact A of the off-normal contacts 42.

The operator now dials the first digit of 2.

two digit number corresponding to the bank position assigned to the contacts of station W. Operation of the dial 1D alternately opensand closes the circuit of relay 24, vibrating the tongue of that relay, thus intermittently opening and closing the previously traced pulsingcircuit.

The switch X is thus stepped vertically so that the wipers are in alignment with a level of their respective banks corresponding to the dialled digit. At the right end of the first series of dial pulses, relay 27 releases, extending the pulsing circuit in parallel to the rotary magnet 33 and to the relay 34.

The operator now dials the second digit, and the resulting series of impulses again causes the pulsing circuit to intermittently open and close, upon which the rotary magnet 33 causes the wipers 4, 5 and 6 to be stepped around a corresponding number of steps. During the stepping of the wipers slow-release relay 34 remains energized, de-energizing only after the wipers have come to rest on the selected bank terminals, and an opportunity has been given to test the condition of the called line.

If subscribers station W is busy, the private bank terminal of the line is grounded over conductor 37 (in a manner previously described) and consequently relay 35 is operated over a circuit extending from the grounded bank terminal, wiper 4, contact C of relay 34, contact D of relay 23, winding of relay 35 to battery. Relay 35 operates over this circuit, and when relay 34 releases, remains looked over a circuit from battery, Winding of relay 35, contact D of relay 23, make-before-break contact E of relay 34, contact C of relay 35, to grounded contact A of relay 25. Operation of relay 35 at its D contact opens the pulsing circuit, previously traced, preventing further operation of the rotary magnet 33. Relay 35 at its A contacts also shortcircuits the upper or high resistance winding of relay 24, thus increasing the current in the dial lead 11, thereby lighting the busy lamp 45, informing the calling operator that the called line is busy.

Upon noticing the lighted busy lamp 45, the operator throws the key 9 to'the right to release the switch X. When the key is thrown to the right, ground is removed from contact B of the key and connected to contact C. This extinguishes the busy lamp 45, and releases relays 12 and 24. The release of relay l2 removes ground from the terminal corresponding to switch X in the lower bank of sequence switch Y, so that switch X is then free to answer a subsequent call.

The release of relay 24 opens the circuit of relay 25, and after an interval the latter relay releases completing a circuit 'for the release magnet 36, which circuit may be traced, from battery, winding of release magnet 36, contact I of relay 23, oil-normal contact C, contact D of relay 25, to grounded contact C of relay 24. The release magnet 36 then operates to restore the switch X to normal. Upon releasing, relay 25 at its A contacts, opens the circuit of relay 35, which thereupon releases. Switch X and all associated relays are now restored to normal. At some later time the operator may again try to establish connection with the called line.

If the called line had been idle, the private bank terminal corresponding to this line would not be grounded. In this case, relay 35 would not operate. Consequently, when relay 34 releases after the second digit series of dial pulses,

with the preselected switch, the test relay being relay 23 will be operated in series with cut-oi! relay 15 to effect operations which have been previously described. In the present case, however, the closure 01 contacts A and C of relay 23 will be without effect as the sequence switch is no longer associated with switch X, and the line circuit, instead of being extended through contact B of switching relay 28, which is now unoperated, is extended through contact C of this relay and contact E of key 9 to grounded negative battery.

The line circuit now extends from negative battery, contact E of key 9, contact C of relay 28, contact G of relay 23, line wiper 5, contact 13 of cut-off relay 15, both windings of polar relay 14, transmitter 16, printer magnets 17, break key 18 to ground. The direction of line current holds relay l4 unoperated. The central station operator then throws key 9 to the left, connecting the line circuit through contact D of key 9, winding of relay 32, transmitter 40 to positive battery, thus reversing the current in the subscribers line 1. This reversal of current causes line relay 14 to close its contact and operate the control relay 19. Operation of the control relay starts the subscribers printer motor 41 and shunts the high resistance winding of line relay 14. The line current is now increased to its normal working value, and as the central station printer motor is running continuously, telegraphic communication can be carried on between the two stations.

When the message has been transmitted, the central station operator can dis-establish the connection by throwing the key 9 to the extreme right. This operation reconnects negative potential to the line, through contact E of key 9, and at contact B, removes ground from the dial lead 11, thus allowing relays 12 and 24 to release. As previously explained, the release of relay 12 conditions the switch X for subsequently answering a calling subscribers line. Release of relay 24, as previously described, effects the restoration of the switch and its associated relays, and also the release of the cut-off relay 15. The release of the cut-off relay reconnects the subscribers line 1 to negative battery through the winding of the line relay 2. Negative potential on the subscribers line 1 (first through the key 9 and later through the line relay 2) causes the line relay 14 at the subscribers station to open its contacts and release the control relay 19. The release of this relay shuts oil the motor 41 and removes the shunt from the high resistance winding of the line relay 14. All circuits are thus restored to normal.

What is claimed is:

1. The combination of a plurality of subscribers lines, a plurality of two-motion switches having access to said lines, a line relay operable when a line calls, a group relay responsive to the operation of the line relay, and a test re-,

lay, common to said switches and associated with a preselected idle switch by the operation of the group relay, for controlling the extent of both motions of said switch.

2. The combination of a plurality of subscribers lines, a plurality of two-motion switcheshaving access to said lines, a test relay common to said switches, a preselector for selecting an idle switch, a line relay operable when a line calls, a group relay, responsive to the operation of the line relay, for associating the test relay thereafter effective to control the extent or both motions of said switch.

3. The combination of a plurality of sub scribers lines, a plurality of two-motion switches having access to said lines, a test relay and an interrupter common to said switches, a preselector for selecting an idle switch, a line relay operable when a line calls, a group relay, responsive to theoperation of the line relay, for

causing the interrupter to control both motions of the preselected switch and the test relay to control the interrupter, whereby both motions of the switch are ultimately controlled by said test relay.

4. The combination of a plurality of subscribers lines, a plurality of two-motion switches acting as combination line finders and connectors having access to said lines, a test relay common to the combination switches for controlling both motions of any switch when the switch is used as a line finder, and a test relay in each switch for controlling one motion of said switch when said switch is used as a connector.

5. The combination of a plurality of subscribers lines, a plurality of two-motion switches having access to said lines, and a test relay common to said switches for controlling the extent of both motions of any switch.

6. The combination of a plurality of subscribers lines, a plurality of two-motion switches having access to said lines, a preselector for selecting an idle switch, a line relay, operable when a line calls, for predetermining the extent of one motion of the switch, a group relay, responsive to the operation of the line relay, for predetermining the extent of the other motion of the switch, an interrupter, and a test relay common to said switches and associated with the selected switch by the operation of the group relay, said interrupter being effective to cause both predetermined motions of the switch, and said test relay being effective to disconnect the interrupter from the switch at the termination of each motion.

7. The combination of a plurality of subscribers lines, a plurality of two-motion switches, a common interrupter for said switches, and a test relay likewise common to said switches for causing the interrupter to start one motion of any switch after the other motion of the same switch has been completed.

8. The combination of a plurality of subscribers lines, a plurality of two-motion switches having access to said lines, a preselector for selecting an idle switch, a line relay, operable when a line calls, for predetermining the motion of said switch in one direction, a group relay, responsive to the operation of the line relay, for predetermining the motion of said switch in the other direction, an interrupter, and a test relay both common to said switches and associated with the selected switch by the operation of the group relay, said interrupter being efiective to cause both predetermined motions of said switch and said test relay being effective to cause said interrupter to start one motion of said switch after the other motion has been completed.

9. The combination of a plurality of subscribers lines, a plurality of two-motion switches having access to said lines, an interrupter common to said switches for effecting both motions of any switch, and a test relay likewise comlines, each switch being provided with two rotary test wipers and a single test relay, a test relay common to said switches, one of said test wipers co-operating with the test relay individual to a particular switch when said switch is operated as a connector, and the other test wiper co-operating with the common test relay when said switch is used as a finder.

FREDERICK G. HALLDEN.

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